Glow-discharge tube



Filed June 10,

INVENTOR SIMON MARI FROUWS United States Patent GLOW-DISCHARGE TUBESimon Mari Frouws, Eindhoven, Netherlands, assignor to North AmericanPhilips Company Inc., New York, N. Y., a corporation of DelawareApplication June 10, 1957, Serial No. 664,750 Claims priority,application Netherlands June 22, 1956 2 Claims. (Cl. 313-497) Thisinvention relates to glow-discharge tubes, in which the main anode andan auxiliary electrode are arranged one at each side of a plate-shapedcathode.

In known tubes, in which the cathode is provided between the anode andthe auxiliary electrode, the latter extends partially into the spacebetween the anode and the cathode through an opening of the cathode, theauxiliary electrode being used as an auxiliary anode. These tubes sufferfrom a disadvantage in that, when applying an alternating voltagebetween the anode and the cathode and the auxiliary anode has a givenpositive bias, a breakdown is able to occur in the wrong sense in themain discharge path even without a control voltage on the auxiliaryanode, which breakdown is initiated by a breakdown between the auxiliaryanode and the main anode.

According to the invention, in a glow-discharge tube in which the mainanode and an auxiliary electrode are located one at each side of theplate-shaped main cathode and the auxiliary electrode extends into anopening of the cathode, this opening is provided with a preferablyconical rim which extends away from the anode and into which thewire-shaped auxiliary electrode extends without projecting from thesurface of the cathode.

By the construction according to the invention it is ensured that theauxiliary discharge is somewhat shielded from the anode field. Thisresults in that no breakdown occurs in the wrong sense in the maindischarge path during the auxiliary discharge at a negative anodevoltage. This permits an alternating voltage of 220 v. 50 c./s. to beapplied between the anode and the cathode with a continuous auxiliarydischarge without the rectitying efiect being lost. Furthermore, thedisadvantage of direct ignition between the anode and the auxiliaryelectrode is obviated. A further advantage is that, in the case of theauxiliary electrode acting as an auxiliary cathode, the auxiliarydischarge extends to and on the wire-shaped auxiliary electrode behindthe cathode (viewed from the anode) with a stronger auxiliary current.As a result, the ignition voltage is not reduced 2,870,365 Patented Jan.20, 1959 'icg more than in the case of a small auxiliary current. Hence,the ignition voltage of the main anode depends less upon the value ofthe auxiliary current than in known arrangements. Even if the auxiliaryelectrode acts as an auxiliary anode this occurs a degree.

In order that the invention may be readily carried into effect, anexample will now be described in detail with reference to theaccompanying drawing, in which Fig. 1 is a vertical cross-sectionthrough the tube and Fig. 2 a horizontal cross-section through thecathode. In Fig. l a number of lead-through pins 2 are sealed into thebottom of a glass bulb 1. A cathode 3 has an opening 4 with a conicalrim into which an auxiliary electrode 5 extends in the form of a thinwire. The supply conductors for the cathode and the auxiliary electrodeare surrounded by glass tubes in order to avoid short-circuits. Thegraphite anode 6 is provided on a supply conductor completely coveredwith enamel 7. The enamel layer is thicker at its end as shown at 8,where an electrode screen 9 is secured to it. A flexible wire 10 issecured to one of the supply conductors and rests against the wall ofthe tube. The wire 10 contacts the layer 12 which is produced on thewall as a result of the cathode disintegration at a high currentdensity. The reference numeral 11 designates a radio-active preparationfor avoiding ignition delays. The cathode and the auxiliary electrodeconsist of molybdenum. The anode screen consists of nickel. The tube isfilled with a mixture of neon and 25% argon at a pressure of 75 mms. Thedimensions of the electrodes and their distances may be derived from thescale shown in the drawing.

What is claimed is:

1. A glow-discharge tube comprising an envelope filled with an ionizablegaseous medium, an anode electrode, a plate-like cathode electrodehaving an aperture therein and an outwardly extending flange-like rimsurrounding said aperture on the side of the cathode remote from theanode, and an auxiliary electrode extending into the aperture in thecathode through said rim-like flange.

2. A glow-discharge tube comprising an envelope filled with an ionizablegaseous medium, an anode electrode, a plate-like cathode electrodehaving an aperture therein and an outwardly extending conicalflange-like rim surrounding said aperture on the side of the cathoderemote from the anode, and an auxiliary electrode extending into theaperture in the cathode through said rim-like flange.

References Cited in the file of this patent UNITED STATES PATENTS2,560,346 Holdaway July 10, 1951 2,560,347 Peck July 10, 1951 2,560,348Stieritz July 10, 1951 2,662,993 Malter Dec. 15, 1953

